From mboxrd@z Thu Jan 1 00:00:00 1970 From: ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org (Eric W. Biederman) Subject: [PATCH review 3/3] proc: Allow proc_free_inum to be called from any context Date: Fri, 21 Dec 2012 20:58:43 -0800 Message-ID: <87sj6yd6nw.fsf@xmission.com> References: <87d2y2elbi.fsf@xmission.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <87d2y2elbi.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> (Eric W. Biederman's message of "Fri, 21 Dec 2012 20:56:49 -0800") List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Oleg Nesterov Cc: Linux Containers , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: containers.vger.kernel.org While testing the pid namespace code I hit this nasty warning. [ 176.262617] ------------[ cut here ]------------ [ 176.263388] WARNING: at /home/eric/projects/linux/linux-userns-devel/kernel/softirq.c:160 local_bh_enable_ip+0x7a/0xa0() [ 176.265145] Hardware name: Bochs [ 176.265677] Modules linked in: [ 176.266341] Pid: 742, comm: bash Not tainted 3.7.0userns+ #18 [ 176.266564] Call Trace: [ 176.266564] [] warn_slowpath_common+0x7f/0xc0 [ 176.266564] [] warn_slowpath_null+0x1a/0x20 [ 176.266564] [] local_bh_enable_ip+0x7a/0xa0 [ 176.266564] [] _raw_spin_unlock_bh+0x19/0x20 [ 176.266564] [] proc_free_inum+0x3a/0x50 [ 176.266564] [] free_pid_ns+0x1c/0x80 [ 176.266564] [] put_pid_ns+0x35/0x50 [ 176.266564] [] put_pid+0x4a/0x60 [ 176.266564] [] tty_ioctl+0x717/0xc10 [ 176.266564] [] ? wait_consider_task+0x855/0xb90 [ 176.266564] [] ? default_spin_lock_flags+0x9/0x10 [ 176.266564] [] ? remove_wait_queue+0x5a/0x70 [ 176.266564] [] do_vfs_ioctl+0x98/0x550 [ 176.266564] [] ? recalc_sigpending+0x1f/0x60 [ 176.266564] [] ? __set_task_blocked+0x37/0x80 [ 176.266564] [] ? sys_wait4+0xab/0xf0 [ 176.266564] [] sys_ioctl+0x91/0xb0 [ 176.266564] [] ? task_stopped_code+0x50/0x50 [ 176.266564] [] system_call_fastpath+0x16/0x1b [ 176.266564] ---[ end trace 387af88219ad6143 ]--- It turns out that spin_unlock_bh(proc_inum_lock) is not safe when put_pid is called with another spinlock held and irqs disabled. For now take the easy path and use spin_lock_irqsave(proc_inum_lock) in proc_free_inum and spin_loc_irq in proc_alloc_inum(proc_inum_lock). Signed-off-by: "Eric W. Biederman" --- fs/proc/generic.c | 13 +++++++------ 1 files changed, 7 insertions(+), 6 deletions(-) diff --git a/fs/proc/generic.c b/fs/proc/generic.c index e064f56..76ddae8 100644 --- a/fs/proc/generic.c +++ b/fs/proc/generic.c @@ -352,18 +352,18 @@ retry: if (!ida_pre_get(&proc_inum_ida, GFP_KERNEL)) return -ENOMEM; - spin_lock_bh(&proc_inum_lock); + spin_lock_irq(&proc_inum_lock); error = ida_get_new(&proc_inum_ida, &i); - spin_unlock_bh(&proc_inum_lock); + spin_unlock_irq(&proc_inum_lock); if (error == -EAGAIN) goto retry; else if (error) return error; if (i > UINT_MAX - PROC_DYNAMIC_FIRST) { - spin_lock_bh(&proc_inum_lock); + spin_lock_irq(&proc_inum_lock); ida_remove(&proc_inum_ida, i); - spin_unlock_bh(&proc_inum_lock); + spin_unlock_irq(&proc_inum_lock); return -ENOSPC; } *inum = PROC_DYNAMIC_FIRST + i; @@ -372,9 +372,10 @@ retry: void proc_free_inum(unsigned int inum) { - spin_lock_bh(&proc_inum_lock); + unsigned long flags; + spin_lock_irqsave(&proc_inum_lock, flags); ida_remove(&proc_inum_ida, inum - PROC_DYNAMIC_FIRST); - spin_unlock_bh(&proc_inum_lock); + spin_unlock_irqrestore(&proc_inum_lock, flags); } static void *proc_follow_link(struct dentry *dentry, struct nameidata *nd) -- 1.7.5.4 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752737Ab2LVE6w (ORCPT ); Fri, 21 Dec 2012 23:58:52 -0500 Received: from out01.mta.xmission.com ([166.70.13.231]:54573 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751506Ab2LVE6u (ORCPT ); Fri, 21 Dec 2012 23:58:50 -0500 From: ebiederm@xmission.com (Eric W. Biederman) To: Oleg Nesterov Cc: Linux Containers , , "Serge E. Hallyn" References: <87d2y2elbi.fsf@xmission.com> Date: Fri, 21 Dec 2012 20:58:43 -0800 In-Reply-To: <87d2y2elbi.fsf@xmission.com> (Eric W. Biederman's message of "Fri, 21 Dec 2012 20:56:49 -0800") Message-ID: <87sj6yd6nw.fsf@xmission.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-AID: U2FsdGVkX1/ph+OkNKWm57UE8qOUTi9bBvPqXInRaEc= X-SA-Exim-Connect-IP: 98.207.153.68 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.1 XMSubLong Long Subject * -3.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% * [score: 0.0000] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa06 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 T_TooManySym_01 4+ unique symbols in subject X-Spam-DCC: XMission; sa06 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Oleg Nesterov X-Spam-Relay-Country: Subject: [PATCH review 3/3] proc: Allow proc_free_inum to be called from any context X-SA-Exim-Version: 4.2.1 (built Sun, 08 Jan 2012 03:05:19 +0000) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org While testing the pid namespace code I hit this nasty warning. [ 176.262617] ------------[ cut here ]------------ [ 176.263388] WARNING: at /home/eric/projects/linux/linux-userns-devel/kernel/softirq.c:160 local_bh_enable_ip+0x7a/0xa0() [ 176.265145] Hardware name: Bochs [ 176.265677] Modules linked in: [ 176.266341] Pid: 742, comm: bash Not tainted 3.7.0userns+ #18 [ 176.266564] Call Trace: [ 176.266564] [] warn_slowpath_common+0x7f/0xc0 [ 176.266564] [] warn_slowpath_null+0x1a/0x20 [ 176.266564] [] local_bh_enable_ip+0x7a/0xa0 [ 176.266564] [] _raw_spin_unlock_bh+0x19/0x20 [ 176.266564] [] proc_free_inum+0x3a/0x50 [ 176.266564] [] free_pid_ns+0x1c/0x80 [ 176.266564] [] put_pid_ns+0x35/0x50 [ 176.266564] [] put_pid+0x4a/0x60 [ 176.266564] [] tty_ioctl+0x717/0xc10 [ 176.266564] [] ? wait_consider_task+0x855/0xb90 [ 176.266564] [] ? default_spin_lock_flags+0x9/0x10 [ 176.266564] [] ? remove_wait_queue+0x5a/0x70 [ 176.266564] [] do_vfs_ioctl+0x98/0x550 [ 176.266564] [] ? recalc_sigpending+0x1f/0x60 [ 176.266564] [] ? __set_task_blocked+0x37/0x80 [ 176.266564] [] ? sys_wait4+0xab/0xf0 [ 176.266564] [] sys_ioctl+0x91/0xb0 [ 176.266564] [] ? task_stopped_code+0x50/0x50 [ 176.266564] [] system_call_fastpath+0x16/0x1b [ 176.266564] ---[ end trace 387af88219ad6143 ]--- It turns out that spin_unlock_bh(proc_inum_lock) is not safe when put_pid is called with another spinlock held and irqs disabled. For now take the easy path and use spin_lock_irqsave(proc_inum_lock) in proc_free_inum and spin_loc_irq in proc_alloc_inum(proc_inum_lock). Signed-off-by: "Eric W. Biederman" --- fs/proc/generic.c | 13 +++++++------ 1 files changed, 7 insertions(+), 6 deletions(-) diff --git a/fs/proc/generic.c b/fs/proc/generic.c index e064f56..76ddae8 100644 --- a/fs/proc/generic.c +++ b/fs/proc/generic.c @@ -352,18 +352,18 @@ retry: if (!ida_pre_get(&proc_inum_ida, GFP_KERNEL)) return -ENOMEM; - spin_lock_bh(&proc_inum_lock); + spin_lock_irq(&proc_inum_lock); error = ida_get_new(&proc_inum_ida, &i); - spin_unlock_bh(&proc_inum_lock); + spin_unlock_irq(&proc_inum_lock); if (error == -EAGAIN) goto retry; else if (error) return error; if (i > UINT_MAX - PROC_DYNAMIC_FIRST) { - spin_lock_bh(&proc_inum_lock); + spin_lock_irq(&proc_inum_lock); ida_remove(&proc_inum_ida, i); - spin_unlock_bh(&proc_inum_lock); + spin_unlock_irq(&proc_inum_lock); return -ENOSPC; } *inum = PROC_DYNAMIC_FIRST + i; @@ -372,9 +372,10 @@ retry: void proc_free_inum(unsigned int inum) { - spin_lock_bh(&proc_inum_lock); + unsigned long flags; + spin_lock_irqsave(&proc_inum_lock, flags); ida_remove(&proc_inum_ida, inum - PROC_DYNAMIC_FIRST); - spin_unlock_bh(&proc_inum_lock); + spin_unlock_irqrestore(&proc_inum_lock, flags); } static void *proc_follow_link(struct dentry *dentry, struct nameidata *nd) -- 1.7.5.4